A generic-type turbocharger is known from EP 1 621 774 A2.
In the case of such turbochargers the piston ring grooves or slots were always arranged in the rotor shaft. In this case, it is possible that one slot per piston ring is provided, or that two piston rings are arranged in one slot. Since the piston ring slot next to the turbine wheel requires a constructional minimum distance from the turbine wheel and the connecting journal on the turbine wheel back is kept axially as short as possible, it has not been possible up to now to introduce two slots in the shaft region without weakening the shaft in cross section or without axially extending the shaft, which has the consequence of very negative effects upon the rotor bearing stability. If the turbine wheel and the rotor shaft are connected by means of a weld, it has not been possible up to now to position the piston ring slots in any desired manner since the region of the weld point is not suitable for the locating of the slots on account of inconsistent material properties.